But as the demands of royal life inevitably take over, the Duke and Duchess of Cambridge will try to strike a balance between creating a relaxed upbringing with that befitting the status of a prince.

As they raise "Georgie" – as grandpa Prince Charles has dubbed him – the young couple will take guidance from how the late Princess Diana managed things, sources say.

"It'll be a carbon copy of how William and Harry were brought up, because of their mother," a friend tells PEOPLE. "However she's painted, her greatest legacy is her sons. The way they've been brought up and the way she taught them to think for themselves and to lead a normal life."

Graham Butland, chief executive of East Anglia Children’s Hospices (a charity Kate works with frequently), agrees: "There's a bit of Diana influence – she brought up William and Harry quite differently to the way that Prince Charles was brought up. And I think there's a natural development as the Royal Family adapts and changes to a different way."

"I don't think Kate will change," he adds. "Having seen her interact with children ... and [overhearing] the conversations that she's had, she’s just so natural. She has a rapport with children."

Kate's demeanor is much like Princess Diana (who died at 36 in 1997), who "adored children of all ages, and understood exactly how to get into a child's mind," her friend Rosa Monckton says.

Monckton – who named Diana her daughter Domenica's godmother – believes the late Princess would have some simple parenting advice for William: "To forget that the world is watching, and to make the most of every single day that they have together."

As a grandmother, Diana would have been playful and supportive.

"She'd have been keen that everything went well with the birth and the first years. And when the baby walks and talks she'd have a good old laugh with him," adds the first friend.

This fall, the Duke, Duchess and Prince of Cambridge will move into Apartment 1a of Kensington Palace – the same location where William and Harry grew up in with their late mother.

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